DNA, genes and chromosomes Flashcards
What does a DNA nucleotide consist of?
Phosphate group, Pentose sugar (deoxyribose), and a nitrogen-containing base
What is the Pentose sugar RNA?
Ribose sugar
What are the 4 bases?
A- adenine, g-guanine, c-cytosine, t-thymine (in RNA this is uracil)
What 2 bases are purines(double-ring structure)?
Adenine & guanine
What 2 bases are pyramidines (single ring structures)?
Cytosine & thymine
How are polynucleotides formed?
Condensation reaction forms a phosphodiester bond between hydroxyl group of one nucleotide and phosphate group of next nucleotide
Describe structure of DNA.
Two polynucleotide strands held together by hydrogen bonds between bases. Bases on each strand complementary to one another. Two strands are anti-parallel and twist around each other to form a double-helix structure.
Give 3 features of DNA
Found in nucleus
Long molecule
Double - stranded
Give 3 features of RNA.
Found in cytoplasm
Relatively short molecule
Single-stranded
Give 3 features of mRNA
Made during transcription
Single poly nucleotide strand
Groups op 3 adjacent bases called a codon
Structure of tRNA
Involved in translation
Single polynucleotide strand folded into clover shape
Hydrogen bonds between specific base pairs hold its shape.
Has a specific sequence of bases called anti-codon at one end.
Have an amino acid binding site on the other end.
Give the features of eukaryotic DNA
-Linear molecule that exist as chromosomes in the nucleus
- wound up around proteins called histones that package and order to DNA form chromosomes
- mitochondria and chloroplasts have their own DNA similar to prokaryotic DNA
Give features of prokaryotic DNA
DNA is circular
Not wound around histones - condenses to fit in cell through supercoiling
What is a gene?
Sequence of DNA bases that codes for a polypeptide chain or functional RNA. Forms primary structure of a protein.
What is a triplet?
Three bases that code for an amino acid
What is functional RNA?
Genes that don’t code for a polypeptide chain.
What is a genome?
Complete set of genes in a cell.
What is a proteome?
Full range of proteins that the cell is able to produce.
What are introns?
Part of genes that don’t code for amino acids
What are exons?
All parts of a gene that code for proteins
What are non-coding repeats?
Non-coding DNA that can be found between genes
Why is DNA replication semi-conservative?
Half the strands in each new DNA molecule are from the original DNA molecule.
Step 1 of DNA replication
Enzyme DNA Helicase breaks hydrogen bonds between bases unwinding DNA to form 2 separate strands.
Step 2 of DNA replication
Each original strand acts as a template strand. Free nucleotides attract to complementary bases on the template strand - A-T G -C
Step 3 of DNA replication
Condensation reactions join nucleotides of new strands. Phosphodiester bonds formed and catalysed by DNA polymerase. Hydrogen bonds form between bases. Each DNA molecule contains a strand from the original DNA molecule.
